TRENTON — The investigation into the George Washington Bridge lane closings hits a critical point today with a court showdown over whether the legislative panel looking into the scandal can get a judge’s order forcing two former advisers to Gov. Chris Christie to turn over records sought under subpoena.

The hearing, scheduled before state Superior Court Judge Mary Jacobson in Trenton, is pivotal because Bridget Anne Kelly and Bill Stepien might hold evidence critical to understanding who orchestrated the September closings.

A ruling in favor of the former advisers would be a major setback to the legislative investigation, said Brigid Harrison, a political science professor at Montclair State University.

"Kelly and Stepien, in particular, are so obviously linked to this that it would be a blow to public perception about the legitimacy of the investigation," Harrison said. "There is a lot riding on the outcome of the hearing."

Christie fired Kelly as his deputy chief of staff in January after emails turned over to the committee revealed she was involved in the decision to close the lanes. "Time for some traffic problems in Fort Lee," she wrote to David Wildstein, a Christie ally at the Port Authority of New York and New Jersey.

At the same time, Christie cut ties with Stepien — his two-time campaign manager who was a consultant for the Republican Governors Association and slated to become chairman of the state Republican Party — because of derisive language used in emails and texts to describe Fort Lee Mayor Mark Sokolich. Many contend the closings were an act of revenge against Sokolich, a Democrat, for not endorsing Christie.

Attorneys for Kelly, who will attend the hearing, and Stepien, who will not, will argue their clients must be shielded from the Legislature’s request because the act of searching for, identifying and turning over records could put them at greater risk of criminal prosecution. In court filings, both have mentioned the ongoing investigation into the bridge scandal by the U.S. Attorney’s office.

They will cite the Fifth Amendment of the U.S. Constitution, which protects citizens from testifying against themselves in criminal cases. More importantly, case law provides protection for people when the actual act of turning over records amounts to self-incrimination.

That protection stems from a 2000 U.S. Supreme Court case, U.S. v. Hubbell, in which the justices agreed with a lower court ruling to throw out an indictment against Webster Hubbell, who was targeted as part of the Whitewater real estate scandal under former President Bill Clinton.

Hubbell was subpoenaed for records and appeared before a federal grand jury, where he asserted his Fifth Amendment right against self-incrimination. He then struck a deal with the prosecution to turn over the records in return for immunity "to the extent allowed by law."

After the records were turned over, the prosecution used them to get a 10-count indictment against Hubbell. The Supreme Court ruled the Fifth Amendment shielded Hubbell from saying incriminating records existed since the prosecution could not independently identify and request them. The immunity deal was upheld and the indictment was dismissed.

In briefs submitted this month, attorneys for Kelly and Stepien argued the subpoenas issued were so broad that it would be necessary for them to actively identify and authenticate the records, which could be used against them by investigators at the U.S. Attorney’s office in Newark.

They also said calls and visits by federal prosecutors and investigators since the September closings was clear evidence that the two were subjects of a criminal investigation. The committee’s attorneys have said the two have failed to prove they are at risk.

James Cohen, a law professor at Fordham University, said a concern over self-incrimination would be interpreted "very liberally," but the more difficult task for Jacobson will be to figure out how providing the various types of documents requested may harm Kelly and Stepien.

She will have to balance the specificity of the subpoena’s request against the actions that would be required of Kelly and Stepien to identify the records and respond. The more specific of a request, he said, the less it requires of the pair and the less chance it would be incriminating.

One solution would be to turn over records but hide the sources of each document, Cohen said. "It’s more than a little tricky. You need to go through several different levels of analysis to figure out what to do."